fix: make installed wheel self-contained + harden install.sh prereqs

Addresses the review on PR #481.

Self-contained wheel (review point 1): the gateway/infra/orchestrator
images build from a context that must hold bot_bottle/, pyproject.toml,
and the root-level Dockerfiles. Modules previously located these by
walking __file__ to the repo root, so an installed wheel (package in
site-packages, no repo root) passed `doctor` but failed `start`.

- Add bot_bottle/resources.py: build_root() returns the repo root in a
  checkout (unchanged) or a staged copy from the wheel's bundled
  _resources/ otherwise; dockerfile()/nix_netpool_module()/
  netpool_script() derive from it.
- setup.py bundles the root Dockerfiles, nix module, netpool script, and
  pyproject.toml into bot_bottle/_resources/ at build; MANIFEST.in ships
  them in the sdist.
- Route every _REPO_ROOT/_REPO_DIR call site (docker/macos launch, macos
  infra, firecracker infra_vm/infra_artifact/setup, orchestrator
  lifecycle/gateway) through resources. Checkout behavior is unchanged.

install.sh prerequisites (review point 2): check for git when installing
a git+ spec, and — before the pip fallback — that pip is usable and the
interpreter isn't externally managed (PEP 668), pointing at pipx.

Tests: test_resources covers checkout + staged-wheel layouts;
test_wheel_install builds the wheel, installs it into an isolated venv,
and asserts `doctor` runs and build_root() yields a valid context.
Running `start` end-to-end still needs a Docker/KVM host (CI).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

bot_bottle/backend/docker/gateway.py

@@ -10,9 +10,10 @@ from ...paths import (
     ORCHESTRATOR_AUTH_JWT_ENV,
     host_gateway_ca_dir,
 )
+from ... import resources
 from ...gateway import (
   Gateway, GatewayTransport, GATEWAY_IMAGE, GATEWAY_NAME, GATEWAY_NETWORK,
-  GATEWAY_DOCKERFILE, REPO_ROOT, GATEWAY_LABEL, MITMPROXY_HOME,
+  GATEWAY_DOCKERFILE, GATEWAY_LABEL, MITMPROXY_HOME,
   DEFAULT_CA_TIMEOUT_SECONDS, CA_POLL_SECONDS, GATEWAY_CA_CERT, GatewayError
 )
 
@@ -50,7 +51,9 @@ class DockerGateway(Gateway):
         # `address` / `stop` work on an already-running gateway without it.
         self._orchestrator_url = ""
         self._gateway_token = ""
-        self._build_context = build_context or REPO_ROOT
+        # Resolved lazily in ensure_built() so merely constructing a gateway to
+        # read its CA never stages a build root from an installed wheel.
+        self._build_context = build_context
         self._dockerfile = dockerfile
         # Ports published on the host (0.0.0.0). Used by the Firecracker
         # backend's dev-harness gateway so VMs can reach it via their TAP link;
@@ -72,9 +75,10 @@ class DockerGateway(Gateway):
         forces a full rebuild (parity with `start --no-cache`)."""
         if self._dockerfile is None:
             return
+        context = self._build_context or resources.build_root()
         argv = ["docker", "build", "-t", self.image_ref,
-                "-f", str(self._build_context / self._dockerfile),
-                str(self._build_context)]
+                "-f", str(context / self._dockerfile),
+                str(context)]
         if os.environ.get("BOT_BOTTLE_NO_CACHE"):
             argv.insert(2, "--no-cache")
         proc = run_docker(argv)

bot_bottle/backend/docker/infra.py

@@ -34,6 +34,7 @@ from .orchestrator import (
     ORCHESTRATOR_NETWORK,
 )
 from ...paths import bot_bottle_root
+from ... import resources
 from ...gateway import (
     GATEWAY_IMAGE,
     GATEWAY_NAME,
@@ -50,8 +51,6 @@ from ...orchestrator.lifecycle import (
 # the pair's public identity.
 INFRA_NAME = GATEWAY_NAME  # the container agents attribute against is the gateway
 
-_REPO_ROOT = Path(__file__).resolve().parents[3]
-
 
 class DockerInfraService(InfraService):
     """Composes the per-host control plane + gateway as two containers.
@@ -68,7 +67,7 @@ class DockerInfraService(InfraService):
         control_network: str = ORCHESTRATOR_NETWORK,
         orchestrator_image: str = ORCHESTRATOR_IMAGE,
         gateway_image: str = GATEWAY_IMAGE,
-        repo_root: Path = _REPO_ROOT,
+        repo_root: Path | None = None,
         host_root: Path | None = None,
         orchestrator_name: str = ORCHESTRATOR_NAME,
         orchestrator_label: str = ORCHESTRATOR_LABEL,
@@ -79,7 +78,9 @@ class DockerInfraService(InfraService):
         self.control_network = control_network
         self.orchestrator_image = orchestrator_image
         self.gateway_image = gateway_image
-        self._repo_root = repo_root
+        # Build context / bind-mount source: the repo root in a checkout, a
+        # staged copy from the installed wheel otherwise (bot_bottle.resources).
+        self._repo_root = repo_root if repo_root is not None else resources.build_root()
         self._host_root = host_root or bot_bottle_root()
         self._orchestrator_name = orchestrator_name
         self._orchestrator_label = orchestrator_label

bot_bottle/backend/docker/launch.py

@@ -33,7 +33,6 @@ from __future__ import annotations
 import dataclasses
 import os
 from contextlib import ExitStack, contextmanager
-from pathlib import Path
 from typing import Callable, Generator
 
 from ...agent_provider import runtime_for
@@ -65,10 +64,7 @@ from ...orchestrator.store.config_store import resolve_teardown_timeout
 from .consolidated_launch import launch_consolidated, deprovision_consolidated
 from .infra import INFRA_NAME
 from .gateway import DockerGateway
-
-
-# Where the repo root lives, for `docker build` context. Computed once.
-_REPO_DIR = str(Path(__file__).resolve().parent.parent.parent.parent)
+from ... import resources
 
 
 def build_or_load_images(plan: DockerBottlePlan) -> BottleImages:
@@ -88,7 +84,7 @@ def build_or_load_images(plan: DockerBottlePlan) -> BottleImages:
             )
         info(f"using cached agent image {plan.image!r}")
         return BottleImages(agent=plan.image)
-    docker_mod.build_image(plan.image, _REPO_DIR, dockerfile=plan.dockerfile_path)
+    docker_mod.build_image(plan.image, str(resources.build_root()), dockerfile=plan.dockerfile_path)
     docker_mod.verify_agent_image(
         plan.image, runtime_for(plan.agent_provider_template).smoke_test,
     )

bot_bottle/backend/docker/orchestrator.py

@@ -15,6 +15,7 @@ import time
 from pathlib import Path
 
 from ... import log
+from ... import resources
 from .util import run_docker
 from ...paths import (
     ORCHESTRATOR_TOKEN_ENV,
@@ -55,8 +56,6 @@ _ROOT_IN_CONTAINER = "/bot-bottle-root"
 
 _HEALTH_POLL_SECONDS = 0.25
 
-_REPO_ROOT = Path(__file__).resolve().parents[3]
-
 
 class DockerOrchestrator(Orchestrator):
     """The control plane as a single fixed-name container. `ensure_built` builds
@@ -71,7 +70,7 @@ class DockerOrchestrator(Orchestrator):
         label: str = ORCHESTRATOR_LABEL,
         port: int = DEFAULT_PORT,
         control_network: str = ORCHESTRATOR_NETWORK,
-        repo_root: Path = _REPO_ROOT,
+        repo_root: Path | None = None,
         host_root: Path | None = None,
         dockerfile: str | None = ORCHESTRATOR_DOCKERFILE,
     ) -> None:
@@ -80,7 +79,9 @@ class DockerOrchestrator(Orchestrator):
         self.label = label
         self.port = port
         self.control_network = control_network
-        self._repo_root = repo_root
+        # Build context / bind-mount source: the repo root in a checkout, a
+        # staged copy from the installed wheel otherwise (bot_bottle.resources).
+        self._repo_root = repo_root if repo_root is not None else resources.build_root()
         self._host_root = host_root or bot_bottle_root()
         self._dockerfile = dockerfile
 

bot_bottle/backend/firecracker/infra_artifact.py

@@ -37,6 +37,7 @@ import urllib.error
 import urllib.request
 from pathlib import Path
 
+from ... import resources
 from ...log import die, info
 from . import util
 
@@ -44,8 +45,6 @@ from . import util
 # scheme can't collide with a cached/published artifact of the old one.
 _ARTIFACT_FORMAT = "1"
 
-_REPO_ROOT = Path(__file__).resolve().parents[3]
-
 # The two per-plane infra VM roles. Each publishes/pulls its own rootfs artifact
 # from its own generic package; the Dockerfiles baked into each differ (only the
 # orchestrator rootfs carries buildah), so the versions are hashed separately.
@@ -74,7 +73,7 @@ def local_build_requested() -> bool:
 
 
 def infra_artifact_version(
-    init_script: str, role: str, *, repo_root: Path = _REPO_ROOT,
+    init_script: str, role: str, *, repo_root: Path | None = None,
 ) -> str:
     """Content hash (16 hex) of everything baked into `role`'s infra rootfs: the
     whole shipped `bot_bottle` package, that role's Dockerfiles, and its guest
@@ -89,6 +88,8 @@ def infra_artifact_version(
     version or a launch host could boot a stale rootfs whose code differs from
     its checkout. `__pycache__`/`.pyc` are the only exclusions — build artifacts,
     never copied."""
+    if repo_root is None:
+        repo_root = resources.build_root()
     h = hashlib.sha256()
     h.update(f"format={_ARTIFACT_FORMAT}\nrole={role}\n".encode())
     pkg = repo_root / "bot_bottle"

bot_bottle/backend/firecracker/infra_vm.py

@@ -42,6 +42,7 @@ from dataclasses import dataclass
 from pathlib import Path
 from typing import Generator
 
+from ... import resources
 from ...log import die, info
 from ..docker import util as docker_mod
 from . import firecracker_vm, infra_artifact, netpool, util
@@ -65,7 +66,6 @@ _GUEST_GATEWAY_JWT_PATH = "/var/lib/bot-bottle/gateway-jwt"
 _GATEWAY_IMAGE = "bot-bottle-gateway:latest"
 _ORCHESTRATOR_IMAGE = "bot-bottle-orchestrator:latest"
 _ORCHESTRATOR_FC_IMAGE = "bot-bottle-orchestrator-fc:latest"
-_REPO_ROOT = Path(__file__).resolve().parents[3]
 
 # Per-role rootfs source image + the extra free space `mke2fs` leaves for the
 # guest to grow into. The orchestrator keeps buildah's large build slack; the
@@ -130,12 +130,13 @@ def build_infra_images_with_docker() -> None:
     orchestrator + buildah). The gateway VM boots the gateway image directly.
     The launch host uses this only in `BOT_BOTTLE_INFRA_BUILD=local` mode;
     `publish_infra` uses it off-host to produce the published artifacts."""
+    root = str(resources.build_root())
     docker_mod.build_image(
-        _ORCHESTRATOR_IMAGE, str(_REPO_ROOT), dockerfile="Dockerfile.orchestrator")
+        _ORCHESTRATOR_IMAGE, root, dockerfile="Dockerfile.orchestrator")
     docker_mod.build_image(
-        _GATEWAY_IMAGE, str(_REPO_ROOT), dockerfile="Dockerfile.gateway")
+        _GATEWAY_IMAGE, root, dockerfile="Dockerfile.gateway")
     docker_mod.build_image(
-        _ORCHESTRATOR_FC_IMAGE, str(_REPO_ROOT), dockerfile="Dockerfile.orchestrator.fc")
+        _ORCHESTRATOR_FC_IMAGE, root, dockerfile="Dockerfile.orchestrator.fc")
 
 
 def build_rootfs_dir(role: str) -> Path:

bot_bottle/backend/firecracker/setup.py

@@ -20,6 +20,7 @@ import subprocess
 import sys
 from pathlib import Path
 
+from ... import resources
 from . import netpool
 from . import util
 
@@ -42,13 +43,13 @@ def _has_systemd() -> bool:
 
 
 def _module_path() -> str:
-    """Absolute path to the importable NixOS module in this checkout."""
-    return str(Path(__file__).resolve().parents[3] / "nix" / "firecracker-netpool.nix")
+    """Absolute path to the importable NixOS module (checkout or wheel)."""
+    return str(resources.nix_netpool_module())
 
 
 def _script_path() -> str:
-    """Absolute path to the bundled bring-up script in this checkout."""
-    return str(Path(__file__).resolve().parents[3] / "scripts" / "firecracker-netpool.sh")
+    """Absolute path to the bundled bring-up script (checkout or wheel)."""
+    return str(resources.netpool_script())
 
 
 def _print_prereqs() -> None:

bot_bottle/backend/macos_container/gateway.py

@@ -28,6 +28,7 @@ from ...paths import (
     ORCHESTRATOR_AUTH_JWT_ENV,
     host_gateway_ca_dir,
 )
+from ... import resources
 from .. import util as backend_util
 from . import util as container_mod
 
@@ -52,8 +53,6 @@ GATEWAY_DAEMONS = "egress,git-http,supervise"
 
 GATEWAY_IMAGE = os.environ.get("BOT_BOTTLE_GATEWAY_IMAGE", "bot-bottle-gateway:latest")
 
-_REPO_ROOT = Path(__file__).resolve().parents[3]
-
 
 def ensure_networks(
     network: str = GATEWAY_NETWORK,
@@ -84,14 +83,16 @@ class MacosGateway(Gateway):
         network: str = GATEWAY_NETWORK,
         egress_network: str = GATEWAY_EGRESS_NETWORK,
         control_network: str = CONTROL_NETWORK,
-        repo_root: Path = _REPO_ROOT,
+        repo_root: Path | None = None,
     ) -> None:
         self.image_ref = image_ref
         self.name = name
         self.network = network
         self.egress_network = egress_network
         self.control_network = control_network
-        self._repo_root = repo_root
+        # Build context: the repo root in a checkout, a staged copy from the
+        # installed wheel otherwise (bot_bottle.resources).
+        self._repo_root = repo_root if repo_root is not None else resources.build_root()
         # Set by `connect_to_orchestrator`: the URL the daemons resolve policy
         # against + the pre-minted `gateway` token they present. The gateway
         # never mints, so it never holds the signing key (#469).

bot_bottle/backend/macos_container/infra.py

@@ -24,6 +24,7 @@ from __future__ import annotations
 
 from pathlib import Path
 
+from ... import resources
 from ...orchestrator.lifecycle import (
     DEFAULT_PORT,
     DEFAULT_STARTUP_TIMEOUT_SECONDS,
@@ -53,8 +54,6 @@ from .orchestrator import (
 # still import it (probe / reprovision attribute against the gateway).
 INFRA_NAME = GATEWAY_NAME
 
-_REPO_ROOT = Path(__file__).resolve().parents[3]
-
 
 class MacosInfraService(InfraService):
     """Composes the per-host orchestrator + gateway containers. Callers use
@@ -70,7 +69,7 @@ class MacosInfraService(InfraService):
         control_network: str = CONTROL_NETWORK,
         gateway_image: str = GATEWAY_IMAGE,
         orchestrator_image: str = ORCHESTRATOR_IMAGE,
-        repo_root: Path = _REPO_ROOT,
+        repo_root: Path | None = None,
         orchestrator_name: str = ORCHESTRATOR_NAME,
         gateway_name: str = INFRA_NAME,
         db_volume: str = ORCHESTRATOR_DB_VOLUME,
@@ -81,7 +80,9 @@ class MacosInfraService(InfraService):
         self.control_network = control_network
         self.gateway_image = gateway_image
         self.orchestrator_image = orchestrator_image
-        self._repo_root = repo_root
+        # Build context / bind-mount source: the repo root in a checkout, a
+        # staged copy from the installed wheel otherwise (bot_bottle.resources).
+        self._repo_root = repo_root if repo_root is not None else resources.build_root()
         self._orchestrator_name = orchestrator_name
         self._gateway_name = gateway_name
         self._db_volume = db_volume

bot_bottle/backend/macos_container/launch.py

@@ -36,7 +36,6 @@ import dataclasses
 import os
 import subprocess
 from contextlib import ExitStack, contextmanager
-from pathlib import Path
 from typing import Callable, Generator
 
 from ...bottle_state import (
@@ -49,6 +48,7 @@ from ...git_gate import GitGate
 from ...gateway.git_gate.http_backend import DEFAULT_PORT as _GIT_HTTP_PORT
 from ...image_cache import check_stale
 from ...log import die, info, warn
+from ... import resources
 from .. import BottleImages
 from ...supervisor.types import SUPERVISE_PORT
 from ..docker.egress import EGRESS_PORT
@@ -71,7 +71,6 @@ from .consolidated_launch import (
     deprovision_consolidated,
 )
 
-_REPO_DIR = str(Path(__file__).resolve().parent.parent.parent.parent)
 _AGENT_SLEEP_SECONDS = "2147483647"
 
 
@@ -94,7 +93,7 @@ def _agent_image(plan: MacosContainerBottlePlan) -> str:
             )
         info(f"using cached agent image {plan.image!r}")
         return plan.image
-    container_mod.build_image(plan.image, _REPO_DIR, dockerfile=plan.dockerfile_path)
+    container_mod.build_image(plan.image, str(resources.build_root()), dockerfile=plan.dockerfile_path)
     return plan.image
 
 

bot_bottle/backend/macos_container/orchestrator.py

@@ -18,6 +18,7 @@ import urllib.request
 from pathlib import Path
 
 from ... import log
+from ... import resources
 from ...paths import ORCHESTRATOR_TOKEN_ENV
 from ...orchestrator.lifecycle import (
     DEFAULT_HEALTH_TIMEOUT_SECONDS,
@@ -45,7 +46,6 @@ _DB_ROOT_IN_CONTAINER = "/var/lib/bot-bottle"
 _SRC_IN_CONTAINER = "/bot-bottle-src"
 
 _HEALTH_POLL_SECONDS = 0.25
-_REPO_ROOT = Path(__file__).resolve().parents[3]
 
 
 class MacosOrchestrator(Orchestrator):
@@ -61,7 +61,7 @@ class MacosOrchestrator(Orchestrator):
         label: str = ORCHESTRATOR_LABEL,
         port: int = DEFAULT_PORT,
         control_network: str = CONTROL_NETWORK,
-        repo_root: Path = _REPO_ROOT,
+        repo_root: Path | None = None,
         db_volume: str = ORCHESTRATOR_DB_VOLUME,
     ) -> None:
         self.image_ref = image_ref
@@ -69,7 +69,9 @@ class MacosOrchestrator(Orchestrator):
         self.label = label
         self.port = port
         self.control_network = control_network
-        self._repo_root = repo_root
+        # Build context / bind-mount source: the repo root in a checkout, a
+        # staged copy from the installed wheel otherwise (bot_bottle.resources).
+        self._repo_root = repo_root if repo_root is not None else resources.build_root()
         self._db_volume = db_volume
 
     def url(self) -> str:

bot_bottle/gateway/__init__.py

@@ -62,7 +62,6 @@ GATEWAY_CA_GLOB = "mitmproxy-ca*"
 # that lands. Env override matches the backend's BOT_BOTTLE_GATEWAY_IMAGE.
 GATEWAY_IMAGE = os.environ.get("BOT_BOTTLE_GATEWAY_IMAGE", "bot-bottle-gateway:latest")
 GATEWAY_DOCKERFILE = "Dockerfile.gateway"
-REPO_ROOT = Path(__file__).resolve().parents[2]
 
 
 def rotate_gateway_ca(ca_dir: Path | None = None) -> list[Path]:

bot_bottle/resources.py

@@ -0,0 +1,159 @@
+"""Locate build-time resources whether bot-bottle runs from a source
+checkout or an installed wheel.
+
+The gateway / infra / orchestrator images are built from a Docker (or Apple
+`container`) build context that must contain the `bot_bottle` package,
+`pyproject.toml`, and the root-level Dockerfiles as siblings. In a source
+checkout that context is simply the repo root, one level above the package.
+An installed wheel has no repo root: the same root-level files are shipped
+inside the package under ``bot_bottle/_resources/`` (see ``setup.py``), and a
+repo-root-shaped build context is staged on demand into the app-data dir.
+
+``build_root()`` is the single source of truth — it returns a directory laid
+out like a repo root (has ``bot_bottle/``, ``pyproject.toml``, the
+Dockerfiles, ``nix/``, ``scripts/``). Every caller that needs a build
+context, a Dockerfile path, the nix netpool module, or the netpool script
+derives from it, so checkout and wheel installs share one downstream path.
+"""
+
+from __future__ import annotations
+
+import fcntl
+import hashlib
+import os
+import shutil
+import tempfile
+from pathlib import Path
+
+from .paths import bot_bottle_root
+
+_PKG = Path(__file__).resolve().parent          # …/bot_bottle
+_CHECKOUT_ROOT = _PKG.parent                     # repo root in a checkout
+_BUNDLED = _PKG / "_resources"                   # wheel-shipped copies
+
+# Root-level files bundled into the wheel under ``_resources/`` (paths are
+# relative to the checkout root, and preserved verbatim under ``_resources/``
+# and in the staged build root). ``setup.py`` copies exactly this set; keep
+# the two lists in sync (``test_resources`` guards that every entry exists).
+BUNDLED_RESOURCES: tuple[str, ...] = (
+    "pyproject.toml",
+    "Dockerfile.gateway",
+    "Dockerfile.orchestrator",
+    "Dockerfile.orchestrator.fc",
+    "nix/firecracker-netpool.nix",
+    "scripts/firecracker-netpool.sh",
+)
+
+# Present at a checkout root, never in a bare installed package — the cheap
+# tell for which layout we're in.
+_CHECKOUT_MARKER = "Dockerfile.gateway"
+
+
+class ResourceError(RuntimeError):
+    """Build resources are missing from the install (corrupt/partial wheel)."""
+
+
+def is_source_checkout() -> bool:
+    """True when running from a source tree (the root Dockerfiles sit beside
+    the package); False from an installed wheel."""
+    return (_CHECKOUT_ROOT / _CHECKOUT_MARKER).is_file()
+
+
+def build_root() -> Path:
+    """A directory shaped like a repo root: ``bot_bottle/``, ``pyproject.toml``,
+    the root Dockerfiles, ``nix/``, and ``scripts/``.
+
+    A checkout returns the repo root itself (no copying). An installed wheel
+    returns a staged copy under the app-data dir, materialized once and reused.
+    The stage is keyed by a digest of the installed package + bundled resources
+    (not the distribution version), so a force-reinstall of a newer commit that
+    keeps ``version = 0.1.0`` still rebuilds instead of reusing a stale tree."""
+    if is_source_checkout():
+        return _CHECKOUT_ROOT
+    return _stage_build_root()
+
+
+def dockerfile(name: str) -> Path:
+    """Absolute path to a root-level Dockerfile, e.g. ``Dockerfile.gateway``."""
+    return build_root() / name
+
+
+def nix_netpool_module() -> Path:
+    """Absolute path to the firecracker netpool NixOS module."""
+    return build_root() / "nix" / "firecracker-netpool.nix"
+
+
+def netpool_script() -> Path:
+    """Absolute path to the firecracker netpool bring-up script."""
+    return build_root() / "scripts" / "firecracker-netpool.sh"
+
+
+def _content_digest() -> str:
+    """A 16-hex digest of the installed package + bundled resources.
+
+    Keys the staged build root by *content*, so a force-reinstall over the same
+    version string (the installer defaults to a git branch + ``pipx install
+    --force``, and ``version`` stays ``0.1.0``) yields a different key and
+    re-stages, rather than reusing an old commit's tree. ``_PKG`` already
+    contains ``_resources``, so walking it covers both."""
+    h = hashlib.sha256()
+    for path in sorted(_PKG.rglob("*")):
+        if not path.is_file() or "__pycache__" in path.parts or path.suffix == ".pyc":
+            continue
+        h.update(str(path.relative_to(_PKG)).encode())
+        h.update(b"\0")
+        h.update(path.read_bytes())
+    return h.hexdigest()[:16]
+
+
+def _stage_build_root() -> Path:
+    """Materialize a repo-root-shaped build context from the installed wheel's
+    bundled resources, keyed by content digest. Idempotent and concurrency-safe:
+    a file lock serializes staging, a partial/stale tree is replaced, and the
+    finished tree is published with an atomic rename."""
+    if not _BUNDLED.is_dir():
+        raise ResourceError(
+            "bot-bottle build resources are missing from this install "
+            f"(expected {_BUNDLED}). Reinstall the package."
+        )
+    base = bot_bottle_root() / "build-root"
+    base.mkdir(parents=True, exist_ok=True)
+    dest = base / _content_digest()
+    if (dest / ".complete").is_file():
+        return dest
+
+    # Serialize staging across processes: a concurrent `start` after an install
+    # must not race on the shared tree. The lock is held only around stage +
+    # atomic publish; the fast path above never blocks.
+    with open(base / ".stage.lock", "w", encoding="utf-8") as lock:
+        fcntl.flock(lock, fcntl.LOCK_EX)
+        if (dest / ".complete").is_file():  # another process staged while we waited
+            return dest
+        # Stage into a private temp dir on the same filesystem, then publish by
+        # rename — never populate a shared path other processes might read.
+        staging = Path(tempfile.mkdtemp(prefix=".staging-", dir=base))
+        try:
+            # The package itself, minus caches and the bundled-resource copies,
+            # so the staged ``bot_bottle/`` matches a checkout's (keeps the
+            # firecracker infra-artifact hash stable across checkout and wheel).
+            shutil.copytree(
+                _PKG,
+                staging / "bot_bottle",
+                ignore=shutil.ignore_patterns("__pycache__", "*.pyc", "_resources"),
+            )
+            # The bundled root files, restored to their checkout-relative layout.
+            for rel in BUNDLED_RESOURCES:
+                dst = staging / rel
+                dst.parent.mkdir(parents=True, exist_ok=True)
+                shutil.copy2(_BUNDLED / rel, dst)
+            (staging / ".complete").write_text("")
+            # Replace any partial leftover for this digest (safe: we hold the
+            # lock), then publish atomically.
+            if dest.exists():
+                shutil.rmtree(dest)
+            os.replace(staging, dest)
+            staging = None  # published; nothing to clean up
+        finally:
+            if staging is not None:
+                shutil.rmtree(staging, ignore_errors=True)
+    return dest